As high-performance rare-earth magnets, there have been known a Sm—Co-based magnet, a Nd—Fe—B-based magnet, and the like. These magnets currently mass-produced contain a large amount of iron (Fe) and cobalt (Co), which contributes to an increase in saturation magnetization. Further, these magnets contain rare-earth elements such as neodymium (Nd) and samarium (Sm), and high magnetic anisotropy is brought about ascribable to behaviors of 4f electrons of the rare-earth elements in a crystal field. This makes it possible to obtain a high coercive force to realize a high-performance magnet.
Such high-performance magnets are used in electric devices such as various kinds of motors, power generators, speakers, and measuring instruments. In recent years, there is an increasing demand for a reduction in weight and a reduction in power consumption of various kinds of electric devices, and in order to cope with this, there is a demand for a higher-performance permanent magnet whose maximum magnetic energy product (BHmax) is improved. When a permanent magnet is used for motors of a hybrid electric vehicle (HEV), an electric vehicle (EV), a railway car, and the like, the permanent magnet is required to have high heat resistance. In a motor for HEV, EV, a railway car, or the like, a permanent magnet whose heat resistance is enhanced by Dy substituting for part of Nd of a Nd—Fe—B-based magnet is used. Since Dy is one of rare-earth elements, there is a demand for a permanent magnet using no Dy in accordance with a large-scale use of motors for HEV and EV.
It is known that the Sm—Co-based magnet exhibits excellent heat resistance without using Dy because of its high Curie temperature. The Sm—Co-based magnet is capable of realizing a good motor characteristic and so on under high temperatures, but a further increase in its coercive force and a further increase in its magnetic flux density are now in need. To increase the magnetic flux density of the Sm—Co-based magnet, it is effective to increase a Fe concentration. However, in a composition range where the Fe concentration is high, the coercive force tends to decrease. Further, the increase in the Fe concentration is likely to cause the generation of a hetero-phase and makes it difficult to obtain a sufficient sintered compact density. These become factors of lowering a coercive force and magnetization. In order to realize a high-performance permanent magnet, there has been a demand for an art to realize both a high coercive force and high magnetization in a Sm—Co-based magnet having a high Fe concentration.